Ask Lemmygrad

The issue here is not that of a single communist being a landlord, but that of the people not all becoming landlords. At the socialist stage, all land belongs to the state and hence the people, thus everyone is a "landlord".

Now back to the pre-revolution capitalist society, it is vital that communists control more land and resources, control more means of production, control more media outlets. If something doesn't belong to a communist, it's safe to say that it isn't in the hands of the proletariat either.

Communists are not capitalist philanthropists, and should not be broke volunteers either. There exists a twisted mindset among some communists that they should be poor or own very little private property while helping the proletariat. Indeed, most of the land and means of production would be seized after the revolution, and many communists would gladly give up their private property at that point, but that doesn't mean that you should have none before. Communists should control as much as they can before the revolution.

If you own more than one house, the extra house can be used for the socialist cause, that includes using it as a base of operations, as a home for people in need, or renting it out as a source of income. The question of being a communist landlord arises if you choose to rent your extra houses. (Selling the house is an option if the funds are then used to empower communists like developing the means of production, or if there is an urgent situation that calls for it.)

There are many scenarios to consider in the case of a communist landlord:

1. Cheap rent to those that "deserve" it.
2. Normal rent to anyone.
3. Expensive rent specifically for high-earning proletariat/petite-bourgeoisie/capitalist.

(I didn't include free rent as that does not involve a source of income.)

In all three scenarios, a communist may indeed feel guilty of robbing or exploiting others, but be aware that we are considering the pre-revolution capitalist society. If you're just going to pocket the money for yourself, then you wouldn't be considered a communist in the first place. Organizing requires time and money/capital. Without Engel's financial aid, Marx wouldn't be able to continue his research. Without revolutionary base areas and the aid of peasants in the rural areas, and without the spirit of self-reliance, the Chinese Communists lead by Mao Zedong would not have succeeded in their revolution.

In conclusion, there's only a problem with being a communist and a landlord if you're living in a capitalist society and not going to use the rent money for the socialist cause.